FDA advisers narrowly vote in favor of Pfizer’s RSV vaccine for the elderly, despite possible safety concerns


During a two-day meeting, vaccine advisers from the US Food and Drug Administration voted to approve RSV vaccines for adults over 60. The candidate vaccines, made by Pfizer and GlaxoSmithKline, could become the world’s first vaccines approved against the common virus.

On Wednesday, committee members voted 10 to 2 in favor of safety and unanimously in favor of the efficacy of GSK’s vaccine for preventing lower respiratory tract disease caused by RSV in the elderly.

For Pfizer’s vaccine, committee members voted Tuesday 7-4 with one abstention that there is adequate data to support the safety and efficacy of the vaccine.

The FDA, which generally follows the committee’s recommendations, is expected to decide whether to approve the vaccines in May, before the typical winter surge of RSV.

Respiratory syncytial virus is a highly contagious virus that causes flu-like illness in people of all ages that increases in severity with age. According to the US Centers for Disease Control and Prevention, RSV is responsible for approximately 177,000 hospitalizations and 14,000 deaths per year in adults 65 years of age or older.

GSK’s RSV vaccine candidate for the elderly was 82.6% effective in preventing lower respiratory tract disease defined by two or more symptoms or and one or more signs or three or more symptoms. The vaccine was 94.1% effective in preventing serious disease.

The Pfizer vaccine was 66.7% effective in preventing moderate lower respiratory tract disease with two or more symptoms and 85.7% effective in preventing disease with three or more symptoms, according to Pfizer.

Although a majority of the committee voted in favor of the vaccines, some committee members expressed concerns about the risk of Guillain-Barré syndrome from both vaccines, a rare neurological disorder in which the immune system attacks its own nerves, causing muscle weakness and sometimes paralysis.

The incidence of Guillain-Barré is approximately 1.5 to 3 cases per 100,000 adults over age 60 in the United States each year, according to the FDA.

Two of 20,000 adults vaccinated in Pfizer’s Phase 3 clinical trial developed symptoms consistent with the rare neurological disorder within nine days of injection.

Of approximately 15,000 vaccinated in GSK’s Phase 3 clinical trial, one man developed Guillain-Barré syndrome within nine days of vaccination.

“It seems to me that a case is a red flag. Two cases are very concerning,” said Dr. Marie Griffin, professor of health policy at Vanderbilt University Medical Center, who voted for the data to show that the two vaccines are effective but not safe.

The FDA has called Guillain-Barré syndrome a “significant potential risk” to Pfizer and recommended that the company conduct a safety study for further evaluation of Guillain-Barré syndrome and other immune-mediated demyelinating conditions. after the vaccine’s potential approval, which the company accepted. . GSK said it would closely monitor cases after approval.

Although Pfizer did not provide data on co-administration with other vaccines, GSK’s data showed potential safety risks when RSV and influenza vaccines were given together.

Two adults in their 60s who received both the flu and RSV vaccine developed acute disseminated encephalitis, a rare neurological disorder that involves swelling of the brain and spinal cord, and one of the individuals died . The FDA considers these cases may be related to RSV or flu vaccination, but a review is ongoing.

“This is a disease with an incidence of 0.1 in 100,000 usually, with the majority being in children and then a dispersal in young adults. So two cases in the elderly within three to four weeks following the vaccine are statistically highly abnormal,” said Dr. Hana El Sahly, chair of the FDA advisory committee, which voted against the GSK vaccine because of its safety profile but in favor. on efficiency.

Dr Adam Berger, who voted in favor of GSK’s vaccine on the basis of safety and efficacy, says this appears to be a problem with co-administration and that concerns about acute disseminated encephalitis and Guillain-Barré syndrome will not find an answer until larger studies are completed. conducted.

“I suggest relying heavily on post-market surveillance and not just trust, but making sure there’s enforcement around the requirements around that,” Berger said. “At the moment, I think the profile appears to be within the acceptable range.”

Some vaccine advisers wanted to see more data on the effectiveness of the Pfizer vaccine in preventing hospitalization or death, especially in people at high risk, including adults over 80, those with comorbidities or those who are immunocompromised.

“I think the data supports the effectiveness of this vaccine, it’s just that the population was underrepresented in people who could benefit the most from the vaccine,” Griffin said of Pfizer’s clinical trial.

The available safety and efficacy data are from the first season of Pfizer’s planned two-season RSV clinical trial and the first of three seasons of GSK’s trial. Some experts want to wait for more data.

“I am desperately looking forward to having a vaccine that works against RSV. It has been a terrible disease throughout my career. I would very much like to see it. No doubt about it,” said Dr. Jay Portnoy, professor of pediatrics at Children’s Mercy Hospital, who voted in favor of GSK’s vaccine but against Pfizer because of its effectiveness.

Portnoy said waiting for a second season of data would provide more robust numbers and full analysis.

“This is not an emergency use authorization. We can take the time to complete the studies and get the information we need before licensing this product in the future. So I remain a bit skeptical given the data we have,” he said.

Others believe that the benefits of candidate vaccines outweigh the potential risks of fatal RSV infection.

“Despite the challenges, despite the additional hurdles, our obligation is to do what is right for the public,” said Dr. Daniel Kim who voted in favor of both plans. “And in this case, we have a bad disease, we have a good vaccine – so far anyway, given the clinical trials – it’s a safe vaccine, and the vaccine can be used to prevent the disease. .”

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